This invention relates generally to the field of rigid disc drives, and more particularly, but not by way of limitation, to an improved head suspension, which is particularly useful with head assemblies incorporating microactuators.
Disc drives of the type known as xe2x80x9cWinchesterxe2x80x9d disc drives or rigid disc drives are well known in the industry. Such disc drives magnetically record digital data on a plurality of circular, concentric data tracks on the surfaces of one or more rigid discs. The discs are typically mounted for rotation on the hub of a brushless DC spindle motor. In disc drives of the current generation, the spindle motor rotates the discs at speeds of up to 10,000 RPM.
Data are recorded to and retrieved from the discs by an array of vertically aligned read/write head assemblies, or heads, which are controllably moved from track to track by an actuator assembly. The read/write head assemblies typically consist of an electromagnetic transducer carried on an air bearing slider. This slider acts in a cooperative hydrodynamic relationship with a thin layer of air dragged along by the spinning discs to fly the head assembly in a closely spaced relationship to the disc surface. In order to maintain the proper flying relationship between the head assemblies and the discs, the head assemblies are attached to and supported by head suspensions or flexures.
The actuator assembly used to move the heads from track to track has assumed many forms historically, with most disc drives of the current generation incorporating an actuator of the type referred to as a rotary voice coil actuator. A typical rotary voice coil actuator consists of a pivot shaft fixedly attached to the disc drive housing base member closely adjacent to the outer diameter of the discs. The pivot shaft is mounted such that its central axis is normal to the plane of rotation of the discs. An actuator housing is mounted to the pivot shaft by an arrangement of precision ball bearing assemblies, and supports a flat coil which is suspended in the magnetic field of an array of permanent magnets, which are fixedly mounted to the disc drive housing base member. On the side of the actuator housing opposite to the coil, the actuator housing also typically includes a plurality of vertically aligned, radially extending actuator head mounting arms, to which the head suspensions mentioned above are mounted. When controlled DC current is applied to the coil, a magnetic field is formed surrounding the coil which interacts with the magnetic field of the permanent magnets to rotate the actuator housing, with the attached head suspensions and head assemblies, in accordance with the well-known Lorentz relationship. As the actuator housing rotates, the heads are moved radially across the data tracks along an arcuate path.
As the physical size of disc drives has decreased historically, the physical size of many of the disc drive components has also decreased to accommodate this size reduction. Similarly, the density of the data recorded on the magnetic media has been greatly increased. In order to accomplish this increase in data density, significant improvements in both the recording heads and recording media have been made.
For instance, the first rigid disc drives used in personal computers had a data capacity of only 10 megabytes, and were in the format commonly referred to in the industry as the xe2x80x9cfull height, 5xc2xcxe2x80x9d format. Disc drives of the current generation typically have a data capacity of over a gigabyte (and frequently several gigabytes) in a 3xc2xdxe2x80x3 package which is only one fourth the size of the full height, 5xc2xcxe2x80x3 format or less. Even smaller standard physical disc drive package formats, such as 2xc2xdxe2x80x3 and 1.8xe2x80x3, have been established. In order for these smaller envelope standards to gain market acceptance, even greater recording densities must be achieved.
The recording heads used in disc drives have evolved from monolithic inductive heads to composite inductive heads (without and with metal-in-gap technology) to thin-film heads fabricated using semi-conductor deposition techniques to the current generation of thin-film heads incorporating inductive write and magneto-resistive (MR) read elements. This technology path was necessitated by the need to continuously reduce the size of the gap in the head used to record and recover data, since such a gap size reduction was needed to reduce the size of the individual bit domain and allow greater recording density.
Reduction of individual bit domain size, along with improved servo systems, allowed for greatly increased track densities, that is the number of data tracks recorded in a given radial region of the disc surface. Disc drives of the current technology are capable of recording and retrieving data with track densities of 10,000 tracks per inch (tpi) or greater, and increases in track density have come to be limited by the mechanical precision of the actuator assemblies used to move the head assemblies from track to track. For instance, as track density approaches 20,000 tpi, mechanical tolerance limitations in the ball bearing assemblies incorporated in the rotary actuator begin to approach the on-track tolerance allowance at the read/write transducers. Piezo-electric actuators have been incorporated in the head mounting arm/head suspension assemblies that allow for repeatable transducer positioning at track densities up to the order of 50,000 tpi, at which point such secondary actuators reach their precision limitations. This limitation has lead to the development of microactuators associated directly with the head assemblies.
Disc drives incorporating such microactuators utilize prerecorded servo information recorded on the disc surfaces to first of all position the rotary actuator described above to the approximate location of the desired data track. The microactuator associated with the individual data head is then used to finely position the head assembly in operative relationship to the data track, and maintain the necessary track following for subsequent data transfers.
Details of the operation of a magnetic microactuator (MAGMA) are disclosed in co-pending U.S. patent application Ser. No. 09/315,006, filed May 19, 1999. Prior art mechanisms related to head suspensions for supporting such head/microactuator assemblies are disclosed in co-pending U.S. patent application Ser. No. 09/306,581, filed May 6, 1999, and PCT Application Ser. No. PCT/US97/21819, filed Nov. 14, 1997. All of the noted applications are assigned to the assignee of the present application and incorporated herein by reference.
The incorporation of microactuators in disc drives, especially in those disc drives which also utilize dynamic loading and unloading of the head, has necessitated modification of the head suspensions used to mount and support the head/microactuator assemblies. In particular, it has become desirable to reduce the pitch attitude stiffness of the gimbal, in order to allow a greater tolerance range in pitch static attitude, leading to higher production yields in the manufacturing process with associated lowered component costs.
It has also been found that, for disc drives incorporating dynamic loading and unloading of the head assemblies, mechanically limiting the movement of the gimbal relative to the load beam of the head suspension assembly aids in providing a robust relationship between the head assemblies and the disc surface at the time of engagement and disengagement between the heads and discs, thus reducing the possibility of damaging head/disc contact or damage to the head suspension.
The present invention provides a head suspension which mounts the head/microactuator assembly in a manner which allows free movement of the head assembly relative to the microactuator, which includes features for reducing pitch attitude stiffness, and features for controlling static attitude of the head/microactuator assembly during head unloading and head loading operations.
The present invention is a head suspension assembly, particularly useful in a disc drive that incorporates a head/microactuator assembly and dynamic loading and unloading of the head/microactuator assembly into and out of operative engagement with a disc. The head suspension includes a gimbal that mounts the head/microactuator assembly via the microactuator, and thus allows the head assembly to be microstepped by the microactuator. The gimbal further includes reverse bending features providing increased pitch attitude compliance, and limiting features which interact with cooperative lifting features on the rigid beam of the head suspension to control the static attitude extremes of the head assembly during dynamic unloading of the head/microactuator assembly from operative engagement with a disc. In a further aspect of the invention, the head suspension includes mechanisms for controlling the attitude of the head/microactuator assembly relative to the disc during dynamic loading of the head/microactuator into operative engagement with the disc.
The manner in which the present invention is implemented, as well as other features, benefits and advantages of the invention, can best be understood by a review of the following Detailed Description of the Invention, when read in conjunction with an examination of the accompanying drawings.